cpufreq: Introduce new relation for freq selection

Introduce CPUFREQ_RELATION_C for frequency selection.
It selects the frequency with the minimum euclidean distance to target.
In case of equal distance between 2 frequencies, it will select the
greater frequency.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/freq_table.c

@@ -117,7 +117,7 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 		.frequency = 0,
 	};
 	struct cpufreq_frequency_table *pos;
-	unsigned int freq, i = 0;
+	unsigned int freq, diff, i = 0;
 
 	pr_debug("request for target %u kHz (relation: %u) for cpu %u\n",
 					target_freq, relation, policy->cpu);
@@ -127,6 +127,7 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 		suboptimal.frequency = ~0;
 		break;
 	case CPUFREQ_RELATION_L:
+	case CPUFREQ_RELATION_C:
 		optimal.frequency = ~0;
 		break;
 	}
@@ -168,6 +169,15 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 				}
 			}
 			break;
+		case CPUFREQ_RELATION_C:
+			diff = abs(freq - target_freq);
+			if (diff < optimal.frequency ||
+			    (diff == optimal.frequency &&
+			     freq > table[optimal.driver_data].frequency)) {
+				optimal.frequency = diff;
+				optimal.driver_data = i;
+			}
+			break;
 		}
 	}
 	if (optimal.driver_data > i) {

include/linux/cpufreq.h

@@ -176,6 +176,7 @@ static inline void disable_cpufreq(void) { }
 
 #define CPUFREQ_RELATION_L 0  /* lowest frequency at or above target */
 #define CPUFREQ_RELATION_H 1  /* highest frequency below or at target */
+#define CPUFREQ_RELATION_C 2  /* closest frequency to target */
 
 struct freq_attr {
 	struct attribute attr;